The research objectives of this project are becoming focused on three major aspects of animal fertilization related to the phenomena of sperm attraction (chemothactic) as it occurs in marine hydrozoa. The research is intended to shed light on the following general problems: 1. What is the mechanism of directed turning of sperm? 2. What are the attracting compounds found in hydroids in terms of properties and molecular structure? a. How does this bear on species specificity? b. How does this bear on the mechanism of attraction? 3. What kinds of interactions occur between sperm penetrating the reproductive organs in animals and the tract epithelial cells, tract secretions, and the female gametes: a. What is the relationship between chemotaxis and sperm interactions with the epithelial cells of the female gonangium in hydroids? b. Does chemotaxis occur during penetration of the female reproductive organs of mammals? c. What is the nature of sperm behavior while moving along the surfaces of epithelia, both in hydroid female gonangia, and in the mammalian reproductive tract? d. What is th nature of the behavioral changes in sperm during penetration in the vicinity of eggs or egg secretions in hydroids? By use of computer analysis of patterns of sperm aggregation and flagellar motion during the approach to the egg; optical studies of sperm swimming on the suface of epithelial cell layers; and preparative purification techniques in organic chemistry.